In:
MRS Proceedings, Springer Science and Business Media LLC, Vol. 465 ( 1996)
Abstract:
For performance assessments of geological disposal of high-level radioactive
waste, activation energies for the diffusion of strontium ions and the basal spacings of compacted sodium montmorillonite in the water-saturated state
were determined. Basal spacings determined by XRD indicated changes in the interlamellar
space from a three-water layer hydrate state to a two-water layer hydrate state as the dry density of the montmorillonite increased from 1.0 to 1.8 Mg
m -3 . Activation energies from 17.3 to 30.8 kJ mol -1 for the apparent diffusion coefficients of strontium ions were obtained. The
lower activation energies than for diffusion of strontium ions in free water were determined for montmorillonite specimens of lower dry density (1.2 Mg
m -3 and below), while the higher activation energies were at
higher dry densities (1.4 Mg m -3 and above). These findings cannot be explained by changes in only the geometric
parameters, which the pore water diffusion model is based upon. Possible explanations for the dry density dependence of the activation energy are the
changes of the temperature dependence of the distribution coefficients and/or of the diffusion process with increasing dry density
Type of Medium:
Online Resource
ISSN:
0272-9172
,
1946-4274
DOI:
10.1557/PROC-465-893
Language:
English
Publisher:
Springer Science and Business Media LLC
Publication Date:
1996
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